What's wrong with my Fusion Drive?

Question

I'm having weird issues with my internal Fusion Drive.

Symptoms:

1. It gave itself a new cryptical name, and I can't change it back
2. In most cases I cannot install new software anymore (e.g. I cannot update Flash)
3. It is sometimes shutting down immediately
4. Disk Utility says "no errors found" but can't mount it.

See below for some screenshots:

Referring to Point 4 and 1 (says: Volume seems to be ok, see the weird name...)

Referring to Point 2 (says: Installation failed)

Error while mounting Flash Player installer image:

26.11.15 10:03:42,000 kernel[0]: hfs: mounted Adobe Flash Player Installer on device disk3s1
26.11.15 10:03:42,082 mds[55]: (Volume.Normal:2464) volume:0x7fb9ef004600 ********** Bootstrapped Creating a default store:1 SpotLoc:(null) SpotVerLoc:(null) occlude:0 /Volumes/Adobe Flash Player Installer
26.11.15 10:03:53,137 authexec[510]: executing /Volumes/Adobe Flash Player Installer/Install Adobe Flash Player.app/Contents/MacOS/Install Adobe Flash Player
26.11.15 10:04:14,000 kernel[0]: hfs: could not initialize summary table for Flash Player
26.11.15 10:04:14,000 kernel[0]: hfs: mounted Flash Player on device disk4s2
26.11.15 10:04:17,000 kernel[0]: hfs: unmount initiated on Flash Player on device disk4s2

diskutil cs list output from Terminal:

CoreStorage logical volume groups (1 found)
|
+-- Logical Volume Group BD4DE488-7C63-4FBA-9FAC-9B92CD56EDE4
=========================================================
Name:         FusionDrive
Status:       Online
Size:         1249060388864 B (1.2 TB)
Free Space:   0 B (0 B)
|
+-< Physical Volume C106FB79-47F5-4967-924F-043C553FC58E
|   ----------------------------------------------------
|   Index:    0
|   Disk:     disk0s2
|   Status:   Online
|   Size:     249715376128 B (249.7 GB)
|
+-< Physical Volume 6492048E-B397-4457-A12B-DA62DD379B35
|   ----------------------------------------------------
|   Index:    1
|   Disk:     disk1s2
|   Status:   Online
|   Size:     999345012736 B (999.3 GB)
|
+-> Logical Volume Family 40A9F389-D3F0-4D75-89A3-36FFAEA6FD57
    ----------------------------------------------------------
    Encryption Status:       Unlocked
    Encryption Type:         None
    Conversion Status:       NoConversion
    Conversion Direction:    -none-
    Has Encrypted Extents:   No
    Fully Secure:            No
    Passphrase Required:     No
    |
    +-> Logical Volume E02059A8-E5D4-4DFF-9D0F-49408380838E
        ---------------------------------------------------
        Disk:                  disk2
        Status:                Online
        Size (Total):          1242500358144 B (1.2 TB)
        Conversion Progress:   -none-
        Revertible:            No
        LV Name:               ´+ßPÜÜÜÜÜPÜ09O8UI9OOOOOOOIOO09O987UUUUZU6T786Z65444RRRR3ERR5EREREREER5R4E43E4ED43ERE3434R43RE3ER4E3R45REW4W45W343E43W424323231QWQ3W3W23432123432323E23E21W23453213E43212R2WEW1221QQ^21
        Content Hint:          Apple_HFS

Output from Terminal for command sudo gpt -r show /dev/disk0

     start       size  index  contents
         0          1         PMBR
         1          1         Pri GPT header
         2         32         Pri GPT table
        34          6         
        40     409600      1  GPT part - C12A7328-F81F-11D2-BA4B-00A0C93EC93B
    409640  487725344      2  GPT part - 53746F72-6167-11AA-AA11-00306543ECAC
 488134984     262144      3  GPT part - 426F6F74-0000-11AA-AA11-00306543ECAC
 488397128          7         
 488397135         32         Sec GPT table
 488397167          1         Sec GPT header

Output from Terminal for command sudo gpt -r show /dev/disk1

     start        size  index  contents
         0           1         PMBR
         1           1         Pri GPT header
         2          32         Pri GPT table
        34           6         
        40      409600      1  GPT part - C12A7328-F81F-11D2-BA4B-00A0C93EC93B
    409640  1951845728      2  GPT part - 53746F72-6167-11AA-AA11-00306543ECAC
1952255368     1269760      3  GPT part - 426F6F74-0000-11AA-AA11- 00306543ECAC
1953525128           7         
1953525135          32         Sec GPT table
1953525167           1         Sec GPT header

My counteractions so far

1. Ran the Apple Hardware Test. Result: nothing found.
2. Ran the First Aid (see screenshot). Result: nothing found.

---

No backup available!

Any help is much appreciated!

---

Follow-up:

The problem while trying to start a Backup you see below. This doesnt make sense, as the external drive has 999gb...

Answer 1

Probably your CoreStorage Logical Volume got corrupted!

I recommend to backup your data to an external drive with Time Machine and rebuild the FusionDrive from scratch.

Time Machine backup

• To backup your main volume, boot to your main drive
• Attach an external drive. The drive (or at least one volume) has to be formatted as an HFS+ Journaled volume. Check this with Disk Utility. If necessary repartition the external drive. All data on the drive will be destroyed after repartitioning/formatting it. The drive (or at least one volume) has to have the size of the volume to back up (or more).

• Usually you will be asked if the external drive should serve as a Time Machine backup drive after plugging it in for the first time. If not, open Time Machine in the System Preferences and configure the external drive as Time Machine backup drive.

  

  Hit Select Backup Drive and choose your external drive:

  

  Turn on Time Machine. The backup will be started after a few minutes and will take some time depending on the size.

Rebuild Fusion Drive

• Boot to Internet Recovery Mode by pressing altcmdR while starting your Mac.
• Booted to Internet Recovery Mode open Utilities → Terminal in the menubar and enter:
  diskutil cs list to get the CoreStorage listing.
• Copy the Logical Volume UUID, it's the fifth listed.
• Now delete the Logical Volume with diskutil cs deleteVolume LVUUID.
  In your case that's diskutil cs deleteVolume E02059A8-E5D4-4DFF-9D0F-49408380838E
• Copy the Logical Volume Group UUID, it's the first listed in the listing of diskutil cs list.
• Then delete the Logical Volume Group with diskutil cs delete LVGUUID.
  In your case that's diskutil cs delete BD4DE488-7C63-4FBA-9FAC-9B92CD56EDE4E
• Enter exit and quit 'Terminal'
• Open 'Disk Utility'. Enter 'Ignore' if you are asked to fix the drives.

• Choose your SSD and partition it: 1 Partition Mac OS X Extended (Journaled), hit the Options button and choose GUID Partiton table and hit OK and Apply.
  Please check that the size is ~250 GB

  Example:

  

• Choose your HDD and partition it: 1 Partition Mac OS X Extended (Journaled), hit the Options button and choose GUID Partiton table and hit OK and Apply.
  Please check that the size is ~1 TB

  Example:

  

• Quit Disk Utility and open Terminal

• Enter diskutil list

  Example (your disk identifiers and sizes are different of course: Your volume SSD probably has the Identifier disk0s2 and the size 250 GB and your volume HDD probably has the Identifier disk1s2 and the size 1.0 TB):

  

• Enter diskutil cs create "Name" IdentifierSSD IdentifierHDD
  In your case probably diskutil cs create "FusionDrive" disk0s2 disk1s2.

  Copy the resulting LVGUUID

  Example:

  

• Enter diskutil cs CreateVolume LVGUUID jhfs+ "FusionDrive" 100%.

  Example:

  

• Enter diskutil cs list
  Check the size of your Logical Volume. It should have the size ~1.250 TB

  Example:

  

• Quit Terminal

• Open 'Disk Utility' and check your newly created volume for errors
• Quit 'Disk Utility'

Restore Time Machine backup

• Attach your external Time Machine backup drive or check this answer if you use NAS or another network share.
• Open 'Restore from Time Machine Backup'
• Choose the appropriate Time Machine backup and restore your system
• Reboot to your restored system.
• Unmount and detach your Time Machine backup drive
• Open 'Terminal' and enter 'diskutil list'
• Check if your 'Recovery HD' is listed.
• If your 'Recovery HD' is missing, usually reinstalling your current system with the latest available system installer (e.g. 'Install OS X Yosemite (10.10.5)' if Yosemite is currently installed) will recreate it without loosing any data.
• After reinstalling the system with the latest available system installer open App Store and install the latest security fixes.

Restore from other sources

If you don't have a Time Machine backup or another appropriate backup, you have to install the system manually.

• Booted to Internet Recovery Mode choose "Restore OS X" (or something similar). This will download and install the original OS X coming with your Mac.

• After installing OS X configure your Mac with your common user. Download and upgrade to the appropriate system (in your case probably 10.10.5). If you haven't "purchased" (it is or was free) OS X Yosemite with your Apple App Store account you are lost and you have to get it from somewhere else.

• After upgrading to OS X Yosemite attach your external drive and open the restore image.
• Copy all necessary files & folders in your old user folder to your new account. Avoid overwriting existing folders of your new account! Also check your old /Users/your_user_name/Library folder (which usually is invisible!).
• Download and reinstall all needed applications.